1. Field of the Invention
The present invention relates to a stereoscopic image display device and more particularly, to a driving circuit unit for a stereoscopic image display device and a driving method thereof
2. Discussion of the Related Art
To provide information accumulated through an information network at high speed, multi-media devices, which are based on digital terminals capable of dealing with letters, sounds and images rapidly, have been researched and developed. Accordingly, a three-dimensional display device has been developed.
In general, the three-dimensional display device displays stereoscopic images using the principle of a stereovision through both eyes. Specifically, parallax between both eyes acts as a primary factor for displaying three-dimensional images. When the right and left eyes look at respective two-dimensional images, the two-dimensional images are transferred to the brain and the brain mixes the two-dimensional images. Thus, a deep and real three-dimensional image is generated.
The above principle is used for three-dimensional display devices displaying three-dimensional images by using two-dimensional images, a stereoscopic display device with specific glasses, a stereoscopic display device without glasses, or a holographic display device. The stereoscopic display device with specific glasses has disadvantages such as inconvenience and unnaturalness due to wearing separate specific glasses. The holographic display device has practicality problems due to using a laser reference beam and a requirement for a large space due to huge equipment. However, the stereoscopic display device without glasses does not require separate specific glasses and its equipment is simple. The stereoscopic display devices without glasses are divided into a parallax barrier type, a lenticular type and an integral photography type. Of these types, presently, the parallax barrier type has been mainly used.
FIG. 1 is a cross-sectional view schematically illustrating a parallax barrier-type stereoscopic image display device according to the related art.
As illustrated in FIG. 1, the parallax barrier type stereoscopic image display device includes a liquid crystal panel 10, a backlight 20 and a parallax barrier 30. The liquid crystal panel 10 includes left-eye pixels L and right-eye pixels R alternating each other. The backlight 20 is disposed at the backside of the liquid crystal panel 10 as a light source and provides light to the liquid crystal panel 10.
The parallax barrier 30 is disposed between the liquid crystal panel 10 and an observer 40. The parallax barrier 30 selectively transmits or blocks light. The parallax barrier 30 includes stripes composed of slits 32 (i.e., transparent portions) and barriers 34 (i.e., opaque portions). The slits 32 and the barriers 34 are alternately arranged such that light from the left-eye pixels L and the right-eye pixels R is selectively transmitted or blocked and thus is provided to left and right eyes of the observer 40.
In the parallax barrier-type stereoscopic image display device, light is emitted from the backlight 20 and is provided to the liquid crystal panel 10. Here, light L1 for the left eye of the observer 40 passes through the left-eye pixels L of the liquid crystal panel 10 and the slits 32 of the parallax barrier 30 to thereby reach the left eye of the observer 40. Meanwhile, light R1 to the right eye of the observer 40 passes through the right-eye pixels R of the liquid crystal panel 10 and the slits 32 to thereby reach the right eye of the observer 40.
Even though it passes through the left-eye pixels L, light L2 for the right eye of the observer 40 is blocked by the barriers 34 of the parallax barrier 30 and does not reach the right eye of the observer 40. Similarly, even though it passes through the right-eye pixels R, light R2 for the left eye of the observer 40 is blocked by the barriers 34 of the parallax barrier 30 and does not reach the left eye of the observer 40.
Accordingly, light passing through the left-eye pixels L reaches only the left eye of the observer 40, and light passing through the right-eye pixels R reaches only the right eye of the observer 40. The observer 40 can see only the light L1 and the light R1. At this time, there is parallax information that the observer 40 may notice between the light L1 and the light R1, and thus the observer 40 can see three-dimensional images.
However, in the parallax barrier-type stereoscopic image display device, since the light L2 and the light R2 are blocked by the barriers 34, a large amount of light is vanished. Therefore, the brightness of the device is decreased.
The parallax barrier-type stereoscopic image display device may have another structure. FIG. 2 is a cross-sectional view schematically illustrating another parallax barrier-type stereoscopic image display device according to the related art. This parallax barrier type stereoscopic image display device switches between two and three-dimensional images.
In FIG. 2, the parallax barrier-type stereoscopic image display device includes a liquid crystal panel 10, a backlight 20 and a parallax barrier 30. The liquid crystal panel 10 includes left-eye pixels L and right-eye pixels R alternating each other. The parallax barrier 30 includes slits 32 and barriers 34 and is disposed under the liquid crystal display device 10. The backlight 20 is disposed under the parallax barrier 30 and emits light toward the parallax barrier 30 and the liquid crystal panel 10. Here, the parallax barrier 30 is disposed between the liquid crystal panel 10 and the backlight 20, and the liquid crystal panel 10 is disposed between the parallax barrier 30 and an observer 40.
Light is emitted from the backlight 20 and passes through the slits 32 of the parallax barrier 30. If the light passing through the slits 32 passes through the right-eye pixels R, the light goes to the right eye of the observer 40. If the light passing through the slits 32 passes through the left-eye pixels L, the light goes to the left eye of the observer 40. In addition, the parallax barrier 30 selectively absorbs and blocks light by the barriers 34 so as to distribute the light emitted from the backlight 20 to the right-eye pixels R and the left-eye pixels L. The parallax barrier 30 may use a liquid crystal panel.
FIG. 3 is a schematic view illustrating a three-dimensional image in a related art parallax barrier type image display device. FIG. 4 is a schematic view illustrating a two-dimensional image in the related art parallax barrier type image display device.
In FIGS. 3 and 4, the parallax barrier type image display device includes a liquid crystal panel 50, and a parallax barrier 60 is disposed under the liquid crystal panel 50. A backlight 70 is disposed under the parallax barrier 60 as a light source.
The liquid crystal panel 50 includes a plurality of pixels. Each pixel includes a thin film transistor and an electrode. Images are displayed by applying an electric field to liquid crystal molecules in each pixel.
As illustrated in FIG. 3, when the device displays a three-dimensional image, right-eye pixels R and left-eye pixels L are alternately arranged in the liquid crystal panel 50.
The parallax barrier 60 may be a liquid crystal panel including a plurality of pixels. Therefore, when a voltage is applied to the parallax barrier 60, some pixels function as barriers 62 absorbing or blocking light emitted from the backlight 70, and the other pixels function as slits transmitting light. The barriers 62 and the slits alternate each other.
Light emitted from the backlight 70 is divided by the barriers 62 and slits of the parallax barrier 60 and passes through the right-eye pixel R or the left-eye pixel L to thereby reach either the right eye or the left eye of observer 80. Accordingly, an image formed by the right-eye pixels R and the left-eye pixels L is provided to the right and left eyes of the observer 80. Because there exists parallax between lights reaching the right eye and the left eye, a three-dimensional image is observable.
In FIG. 4, a voltage is not applied to the parallax barrier 60, and barriers and slits are not formed in the parallax barrier 60. Every pixel of the parallax barrier 60 transmits light. Therefore, the right-eye pixels and the left-eye pixels are discriminated in the liquid crystal panel 50, and the same images are provided to the right eye and the left eye of the observer 80. Accordingly, a two-dimensional image is displayed.
In the stereoscopic image display device, to display two and three-dimensional images smoothly, response time of the liquid crystal molecules in the parallax barrier should be short.